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Equine Infectious Anemia: Viral infections of the hematopoietic system -…
Equine Infectious Anemia: Viral infections of the hematopoietic system
basics
aka "swamp fever"
worldwide distribution
high prevalence in coastal US
seroprevalence can be as high as 70%
affects
equids
horses
donkeys
mule
:warning: REPORTABLE
fatal
may be asymptomatic
agent characteristics
retrovirus
lentivirus
lifelong persistent infection
integrates into host genome
Abs present = infected
enveloped
positive sense RNA
present in all tissues
but it has favorites
macrophages
dedritic cells
endothelial cells
spreads via monocytes
:red_cross: not in CD4 lymphocytes
easily killed by disinfectants + detergents
incubation 1-3w, as long as 1-4 mo
pathogenesis
disease forms
acute
high fever (>105F)
non-specific signs 2-3w post-exposure
virus actively replicating
may be fatal
short (<24hr)
chronic
animal alternates between remission and disease
animal loses condition
"swamper"
antigenic drift and new env proteins during viremic episodes
followed by robust immune response
inapparent
asymptomatic
infectious reservoir
low [virus] in blood
stress may convert to acute form
donkey and mules
infectious dose (ID) is 10^3 viruses
clinical signs
measurements
:female-doctor:
tachycardia
tachypnea
fever
:microscope:
transitory anemia
perivascular lymphoid infiltrations
proliferative glomerulonephritis
IgG deposition
deposition of complement
thrombocytopenia
esp. after acute febrile episode
causes petechial hemorrhages
increased IgG and IgM
IMHA
immune complexes bind Ag on RBC and cuse hemolysis
may or may be present
diagnostic tests
inoculation
agar gel immunodiffusion (AGID)
ELISA
(competitive ELISA) cELISA
detects p26 Ag
synthetic Ag ELISA (SA-ELISA)
detects gp45
p26 Ag
serum needed
false + risk
must confirm with AGID or immunoblot
immuno-blot
:sports_medal:
Coggin's
false positives
foal w/ passive Ab
false negative
recently infected
Ab negative for 2-3w
RT-PCR
best for foal with maternal Abs
screening blood donors
confirm sero tests
in cases of suspected vertical transmission
virus isolation
:eye:
depression
weakness
:hand:
ventral pitting edema
petechiae
epistaxis (nosebleeds)
jaundice
differential diagnosis
equine viral arteritis
purpura hemorrhagica
leptspiraosis
babesiosis
severe strongyliasis
phenothiazine toxicity
autoimmune hemolytic anemia
transmission
biting flies
don't travel more than 100m
transplacental
lacogenic
iatrogenic
semen
not a zoonotic risk
when to test
competitive shows/events
interstate transport
changing ownership
auctioned
symptomatic
positive diagnosis in herd
annual exam
positive test action plan
report to state vet
permanently ID the horses
brand
tattoo
USDA ID!
advise on final destination
euthanasia
federally inspected slaughter facility
federally approaved research facility
permanent quarantine on property of origin
keep >200 yards from other horses
prevention
fly control
client edu
yearly testing
no vaccine
test and isolate at-risk herds
require negative Coggin's tests
disinfect items in contact with horse's blood